Cracking catalyst and method of use



United States Patent 3,220 944 CRACKING CATALYST AND METHOD OF USEAlfred E. Hirschler, Springfield, Pa., assignor to Sun Oil Company,Philadelphia, Pa., a corporation of New Jersey No Drawing. Filed Mar.16, 1965, Ser. No. 440,295 4 Claims. (Cl. 208-120) This application is acontinuation-in-part of my copending application Serial No. 129,984,filed August 8, 1961.

This invention relates to a process for cracking hydrocarbons utilizingnovel catalyst compositions having improved cracking activity.

Amorphous synthetic silica-aiumina catalysts are widely used to promotethe cracking of hydrocarbons. It has now been found that the crackingactivity of this type of catalyst or of the acid treated natural claycatalysts can be substantially increased by ion exchanging the catalystwith aqueous salt solutions containing certain metal ions, namely,cuprous copper, silver or aurous gold. Any of these metals whenincorporated in the lattice of the catalyst in minor amount generally inthe range of 0.15.0% by Weight by ion exchange unexpectedly causes amarked increase in the catalytic activity of such silica-aluminacatalysts.

Preparation of the catalyst compositions utilized in crackinghydrocarbons according to the invention is carried out by treating aconventional silica-alumina catalyst with an aqueous solution of asilver salt, an aurous gold salt or a cuprous copper salt in a manner toeffect ion exchange and to incorporate the metal ion from the solutioninto the lattice of the catalyst. Cupr-ic copper and auric gold saltscannot be used in practicing the invention, since when incorporated inthe catalyst by ion exchange they have the effect of decreasing thecatalytic activity. Mixed salts of the specified metals can be used ifdesired. The anion portion of the salt employed is immaterial as long asthe salt is sufliciently water soluble, since by the method ofpreparation the anion does not become incorporated in the catalyst.Examples of salts which can be used for ion exchange with thesilica-alumina catalysts are silver nitrate, silver acetate, cuprouschloride, cuprous ammonium formate, cuprous acetate and cuprous ammoniumacetate. Aurous salts such as aurous chloride tend to be too insolublefor use as such, but sufficient aurous ions can be obtained in solutionby complexing the aurous salt with ammonia or amines.

The procedure of preparing the catalyst involves admixing asilica-alumina cracking catalyst with a relatively large volume of anaqueous solution of an appropriate salt, as specified above, andagitating the mixture for a time suificient to permit ion exchange totake place. The concentration of salt in the treating solution can varywidely but generally a dilute solution such as 0.1-2.0 molar is used.The treatment can be done at room temperature or elevated temperaturescan be used to expedite the ion exchange reaction. The time of contactof the aqueous solution can vary widely, e.g., from minutes to 10 hours.After the treating solution has been drained from the catalyst, thetreatment can be repeated one or more times with additional amounts ofthe aqueous solution to insure the incorporation of a suflicient amountof metal ion in the catalyst lattice. It is not certain just what ion orions from the silica-alumina catalyst composition exchange with themetal ions from the solution but it appears likely that the transfer atleast in part involves a replacement of hydrogen ions by the metal ions.

An alternative procedure for effecting the ion exchange 3,220,944Patented Nov. 30, 1965 involves placing the silica-alumina catalyst in acolumn and percolating the salt solution through the column. This methodgenerally provides for more efficient utilization of the salt.

After the ion exchange reaction has been effected, the treated catalystis washed one or several times with a relatively large volume of waterto remove all of the treating solution not drained from the catalyst.This also insures removal of all of the exchange ions that have beendisplaced from the catalyst. Hence the present procedure differs fromprior art procedures in which a catalyst base has been impregnated witha treating agent and then dried and calcined, thus leaving all of thetreating agent and all components from the catalyst base in the finallcomposition. The washed catalyst is finally dried and calcined to obtainthe composition used according to the present invention.

From the foregoing it can be seen that the catalysts used in crackinghydrocarbons according to the present invention are amorphous syntheticsilica-alumina catalysts or acid treated clay catalysts in which some ofthe original ions within the lattice thereof have been displaced bymetal ions which are either silver, cuprous copper or aurous gold.Generally the amount of such metal ion incorporated in the finalcomposition is 0.1-5.0% by weight. The silica-alumina starting materialcan be amorphous synthetic silica-alumina, silicaalumina-thoria,silioa-alumina-magnesia or silica-aluminazirconia or can be acid treatedsiliceous clays such as montmorillonite and kaolin. The silica-aluminacatalyst can be either calcined or uncalcinated prior to the ionexchange reaction.

Catalysts prepared in the foregoing manner have markedly increasedactivities for the conversion of hydrocarbon cracking stocks bycatalytic cracking, as compared to the original silica-aluminacomposition. The catalyst can be used to effect the cracking reactionunder conventional hydrocarbon cracking conditions including atemperature in the range of 375-550" C.

The following examples illustrate the invention more specifically:

Example 1 A one molar aqueous solution of AgNO was prepared bydissolving 76.5 g. of the salt in 450 ml. of Water. 50 g. of acommercial silica-alumina catalyst having an alumina content of about12% by weight and a mesh size of 60-210 (U.S. Sieve Series) was treatedwith the solution in three steps using one-third of the solution in eachstep. The treatment involved stirring the catalyst with ml. of the AgNOsolution for 4 hours, filtering the solution from the catalyst andrepeating this procedure two more times. The catalyst was thenthoroughly Washed with water, dried and calcined at 500 C. Analysis ofthe treated catalyst showed that it contained 2.6% silver by weight.This is equivalent to 0.26 meq. of Ag ion per gram of catalyst. Theactivity of the catalyst for cracking cumene was tested as hereinafterdescribed.

Example 2 A one molar aqueous mixture of cuprous chloride was preparedby adding 74.3 g. of Cu Clto 750 ml. of water. 30 g. of the samesilica-alumina catalyst as in Example 1 was treated three successivetimes using 250 ml. of the Cu Cl -water mixture each time. In this caseonly part of the salt was dissolved in the water due to its lowsolubility. The treated catalyst was washed sufficiently with water toremove all the Cu Cl not consumed by ion exchange, and the washedcatalyst was dried and calcined. Analysis showed that the treatedcatalyst contained 1.9% copper by weight, equivalent to 0.30 meq. ofcuprous ion per gram. Its cracking activity was also determined.

Each of the foregoing compositions was tested as a catalyst forpromoting the cracking of cumene. The catalyst was used as a fixed bedin a flow reactor, and the liquid hourly space velocity was 50. Theresults as listed in the accompanying table are for the average reactionproduct during one hour operation. Runs were also made using theuntreated silica-alumina for com- From the tabulated data it can be seenthat each of the metal ions caused a substantial increase in theactivity of the silica-alumina catalyst. At 440 C., the silver ioncaused the conversion to increase from 13.6% to 31.2% corresponding toan activity increase of about 130%. At the same temperature the copperion caused an activity increase of 67%. While not specifically shown,the aurous gold ion likewise results in marked increase in crackingactivity.

The cracking of cumene is merely illustrative of the improvementeffected in the cracking of hydrocarbons by means of the presentinvention. Similar improvements are attained in the cracking of otherhydrocarbon stocks such as parafiins or gas oils.

I claim:

1. Method of cracking a hydrocarbon cracking stock which comprisescontacting said stock at a tempenature in the range of 375-550" C. witha catalyst composition consisting essentially of a silica-aluminacracking catalyst selected from the group consisting of amorphoussynthetic silica-alumina, amorphous synthetic silica-aluminathoria,amorphous synthetic silicaaalumina-magnesia, amorphous syntheticsilica-alumina-zirconia, acid treated montmorillonite and acid treatedkaolin, said catalyst having incorporated therein by ion exchange ametal ion selected from the group consisting of ions of cuprous copper,silver and aurous gold, the amount of said metal incorporated into thecatalyst by ion exchange being 0.l-5.0% by weight of the compositionwhen dried and calcined.

2. Catalyst composition according to claim 1 wherein said metal ion iscuprous copper.

3. Catalyst composition according to claim 1 wherein said metal ion issilver.

4. Catalyst composition according to claim 1 wherein said metal ion isaurous gold.

References Cited by the Examiner UNITED STATES PATENTS 2,258,786 10/1941Melaven et a1. 208119 2,464,205 3/ 1949 Bates 208-l20 3,073,777 1/1963Oettinger 208111 DELBERT E. GANTZ, Primary Examiner.

1. METHOD OF CRACKING A HYDROCARBON CRACKING STOCK WHICH COMPRISESCONTACTING SAID STOCK AT A TEMPERATURE IN THE RANGE OF 375-550*C. WITH ACATALYST COMPOSITION CONSISTING ESSENTIALLY OF A SILICA-ALUMINA CRACKINGCATALYST SELECTED FROM THE GROUP CONSISTING OF AMORPHOUS SYNTHETICSILICA-ALUMINA, AMORPHOUS SYNTHETIC SILICA-ALUMINATHORIA, AMORPHOUSSYNTHETIC SILICA-ALUMINA-MAGNESIA, AMORPHOUS SYNTHETICSILICA-ALUMINA-ZIRCONIA, ACID TREATED MONTMORILLONITE AND ACID TREATEDKAOLIN, SAID CATALYST HAVING INCORPORATED THEREIN BY ION EXCHANGE AMETAL ION SELECTED FROM THE GROUP CONSISTING OF IONS OF CUPROUS COPPER,SILVER AND AUROUS GOLD, THE AMOUNT OF SAID METAL INCORPORATED INTO THECATALYST BY ION EXCHANGE BEING 0.1-5.0% BY WEIGHT OF THE COMPOSITIONWHEN DRIED AND CALCINED.